Process for the preparation of organic acids



Patented May 5, 1936 UNITED STATES PATENT OFFICE raocsss roa rm: raaraaarrox or oaoamo acms Alfred 'r. Larson, Wilmington, m, 'alaignor to E. I. du Pont de Nemours & Company, Wil- Del., a corporation of Delaware No Drawing. Application October 25, 1983,

Serial No. 639,481

'IOlalms.

the interaction oi. aliphatic alcohols and carbon monoxide in the presence of a catalyst.

It is lmown that-organic acids and esters can be prepared by the interaction, in the vapor or liquid phase, of organic compounds with the oxides of carbon. For example, it has been shown that by the condensation of methyl alcohol with carbon monoxide in the presence of a suitable catalyst, acetic acid, methyl acetate, and methyl formate may be prepared in proportions which are governed by the particular operating conditions.

An object of this invention is to provide improvements in processes for the preparation of higher molecular weight organic compounds thru the introduction of carbon monoxide into the lower molecular weight organic compounds. A further object of this invention is to provide a process for the preparation of monocarboxylic acids by the condensation of an aliphatic alcohol with a carbon oxide in the presence of a cat- 85.alyst. Another object of this invention is to provide a process for the preparation of acids having the structural formula: CnHIn-HCOOH- from alcohols having the structural formula: CnHm+1OHby subjecting the alcohols to the 80 action of the carbon monoxide in the presence of a halogenated aliphatic or aromatic hydrocarbon such as propyl chloride, benzyl chloride, etc. with or without the presence of an absorbent material such as pumice, silica gel, active carbon, etc. Other objects will hereinafter appear.

The above objects can be realized by passing a vaporized aliphatic monohydroxy alcohol, carbon monoxide, and a halogenated hydrocarbon,

under suitable pressure and temperature conditions, over active carbon or more particularly over activated charcoal; The products resultingfrom such a reaction will contain generally a mixture of, among other compounds, aliphatic 45 carboxylic acids some of which have a greater, some a lesser, number of carbon atoms than are present in' the alcohol treated,-an aliphatic acid containing one more carbon atom than the alcohol, usually. predominating.

80 The halogenated hydrocarbons which are suit able for activating the reaction include the halides of methane,--that is the mono-, di-, and tri-chlorides, bromides, or iodides of methane, carbon tetra-halides being included as, for exll ample, carbon tetrachloride; the halogenated derivatives of the higher hydrocarbons and including more particularly the ethyl halides, the normal and iso-propyl halides, the butyl halides, including such compounds as the l-iodo and 2- iodo-butane, and the Z-methyl-idoand 2- 5 methyl-2-iodo-propane as well as the other halides of these compounds; the ethylene, the ethylidine and propylene halides; tri-chlor-hydrin, perchloroethane, and the unsaturated halogenated hydrocarbons, more particularly the 10 allyl chlorides and bromides, and similar halides such as vinyl halide, alpha-halogenated propylene, trichlorethylene, acetylene tetrachloride, and homologous compounds. Any of the halogenated hydrocarbons, whether saturated or un- 18' saturated, are suitable as catalysts for this re-- action particularly when used in conjunction. with a form of active carbon.

The alcohol-carbon monoxide reaction which can be accelerated by the above described cat- 90 alysts may be expressed as follows:

In accordance with the particular operating conditions, it will be found that, in some instances, 5 the acid may not be formed directly in the free state, but may be produced as the ester of the alcohol. The alcohols used may be replaced, if desired, wholly or partly by the corresponding alkyl ethers oi the alcohols, such as dimethyl an ether, diethyl ether, or the mixed alkyl ethers, the alkyl esters, the alkyl amines, or the alkyl halides. Experts in this art know that it is advantageous, altho not essential, to have water vapor present during the methanol-carbon mon- 35 oxide to acetic acid reaction. This is true also when the reaction is conducted with compounds which decompose to give the alcohol and is especially advantageous when the compound is such that it forms the alcohol by hydrolysis. 40

The synthesis can generally be efilciently carried out under the following operating conditions. The pressure may vary from approximately 25 atmospheres to 900atmospheres or higher with the preferable operating range in the neighborhood of 350-700. atmospheres. These pressurs do not diflfer materially from those used when other types of 'catalysts are employed for this synthesis nor do the temperatures vary appreciably from those already known for reactions of this type. For example, the process can be suitably carried out, with our catalyst, at temperatures of between 200400 0., but still higher or lower temperatures may also be used in some cases, the speed of the reaction M11855 aoaavaa 3 acid which comprises contacting proyl alcohol, carbon monoxide and carbon tetrachloride with activated charcoal.

7. A process for the preparation of acetic acid which comprises reacting a gaseous mixture containing in approximately the precentages given, 85% carbon monoxide, 5% methanol, 5% water vapor, and 5% hydrogen, in the presence of 0.125% carbon tetrachloride and activated charcoal, the reaction being conducted at a temperature and pressure of approximately 325 C. and 700 atmospheres respectively.

swamp 'r. LARSON. 

